Magnetic bubble domain devices are well known in the art. There are two basic types of devices depending upon the method by which bubbles are propagated in bubble devices; the first is the field access type and the second is the current (or conductor) access type. The most familiar mode of operating a magnetic bubble device is termed the "field-access" mode. In this mode, a pattern of magnetically soft elements (such as Permalloy) is formed in a plane adjacent a layer of material in which the bubbles are moved. Another technique uses ion-implantation in the bubble layer to form a pattern of contiguous disks. The bubble layer is typically a thin magnetic garnet film disposed on a suitable non-magnetic substrate. A magnetic field is generated in the plane of the layer and the field caused to reorient to incrementally-offset radial positions cyclically in the plane. Each element is so shaped that various portions thereof respond to in-plane field to generate pole-patterns which change as the field precesses. The configuration of adjacent elements sets up a sequence of travelling potential wells in the layer which causes bubble movement.
In current access devices, the necessary potential wells are provided by a set of conductor patterns in which polyphase, usually two or three phase, currents are transmitted. The conductors are typically formed in multiple layers, insulated from one another and driven in a two or three phase manner. An example of such a device is described in U.S. Pat. No. 3,460,116.
Various types of magnetic bubble domain device architectures are known in the prior art, one of the best known being the major loop/minor loop configuration. The major loop/minor loop configuration, such as described in U.S. Pat. No. 3,618,054, consists of a plurality of first recirculating "minor" channels and a second "major" channel.
Bubble replication is achieved in permalloy field access bubble devices by stretching the bubble then cutting it into two parts, one part is left in the primary track and the second is transferred to the secondary tracks. The bubble stretching is performed either by applying a high current pulse to the same conductor used for cutting the bubble or by utilizing some large size permalloy propagation elements such as the pickax element. Ion-implanted field access devices, however, lack the strong wide pole distribution necessary for stretching bubbles for successful replication over adequate bias range. Prior to the present invention, there has been a replicated design based upon the stretching action of a conductor together with a cutting action of the charged wall. Such configurations such as is known from the Nelson et al publication, "Ion-Implanted Bubble Circuit Design", 1980 Intermag, Boston, Paper 22-2. In such configurations the bias for face margins for replication are relatively narrow and the long term reliability of the passive charged wall may be disadvantageous in certain applications. There has, therefore, not been a simple and reliable replicator for use with ion-implanted devices which does not rely upon the stretching action of a conductor.